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Searching around the last couple days for anything else I may get done to the P08 head before I have all my stuff to put it back together and HOPEFULLY never have to remove it unless I want to.. I read in an older post of some build that the D16Z6 would potentially benefit from a bit of valve unshrouding. Looking into WHAT that was turned up lots of info, just not on Hondas. Looking at the CC on my head, I do see where some improvement can be made but is it really bad enough? Are the CC walls here too close for comfort?
Anyone with some more port/machinist info, experience, etc please chime in! I know there's lots of B-series runners here and those combustion chambers, stock for stock, look like hell compared to mine. I expected to see WAAAYYY more casting flaws than I cleaned up just from comparison...
Anyhow.. below is a decent shot showing my shrouding as is and uncut. (Havent tried to open them up at all yet).
(We've actually got a D build sitting here now for fab that I specced the motor for a little over 5 years ago, I'll have to make a thread in a few days)
(We've actually got a D build sitting here now for fab that I specced the motor for a little over 5 years ago, I'll have to make a thread in a few days)
Signs point toward a fairly simple DIY task on this. Well, compared to the likes of porting and polishing, Unshrouding is pretty straightforward. But from the Chevy and Ford heads I've seen in need of unshrouding, the head I am working with more resembles a small block head AFTER procedure. What engine wouldn't benefit from better flow? Lol! I hadn't seen much at all in regards to Dseries doing this. I looked to have been talked about but that was the extent. The only bit I found that made reference to an unshrouded Z6 did not go into much detail, just said it was beneficial. Figured I would drum up some more insight here.
oh yeah, post that build thread!!
Looking here, this is the stock bore headgasket, i have 1mm of room to tinker with before the gasket threatens to overhang into the CC. Now, it will be a 76mm gasket so technically, I'll have 2mm space. I have marked out already the material that could be removed with a sharpie. Turns out it is juuuuust a bit over 1mm around the shroud, but when the larger gasket is put on, it won't hang over into the chamber. I would think that removing 1mm worth of material between the cc wall and valves would net a decent result. Thoughts?
If you have all the valves out I would at the least blend the valve seat and ports together. The core shift causes a bit of a ridge on some or most ports transitioning to the valve seat. It's the easiest way to gain flow and doesn't require much skill just a few flapper bits and a dremel tool.
If you have all the valves out I would at the least blend the valve seat and ports together. The core shift causes a bit of a ridge on some or most ports transitioning to the valve seat. It's the easiest way to gain flow and doesn't require much skill just a few flapper bits and a dremel tool.
Ooohhh.. Good catch! Hadn't thought about that. From the article posted here and the formula for valve flow, it doesn't take the shroud into consideration for flow itself but seems that would affect more for how it flows rather than how much. So unshrouding would cause less restriction to the air already passing through. Maybe less turbulence? There should be **some** from my understanding?
From the looks of it the valves are pretty well unshrouded from the factory. I would spend the time blending the valve seats instead. You will make more gains there and not have to worry about making sure all combustion chambers are shaped identically.
11-14-2018, 03:04 AM
D16Z6 valve unshrouding: worth it?
